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DNT: From pop bottles to pharmaceuticals

What if we could turn millions of plastic pop bottles back into chemicals, and then reuse those chemicals in things such as pharmaceuticals or cosmetics?

Turns out that's exactly what students at two Wisconsin schools have shown can be done.

Research teams of undergraduate students working with Nick Robertson, assistant professor of chemistry from Northland College in Ashland, and Michael Carney, a professor at the University of Wisconsin-Eau Claire, developed a method for turning used plastic into useful molecules for high-value products.

Their work appears in the March issue of the prestigious journal Chemical Communications.

Plastic bottles are made out of refined petroleum, or oil. Petroleum-based polymers such as polyesters and polycarbonates make up a significant proportion of the 100 million tons of plastic waste generated globally each year.

No firm numbers are available, but it's estimated that at least 200 billion plastic bottles, 58 billion disposable cups and hundreds of billions of plastic bags are trashed annually.

In essence, the Wisconsin researchers deconstructed the plastic bottle and captured useful chemical molecules from the plastic -- molecules that could be reformed as the precursors to an antibiotic drug or the base for cosmetics.

Currently, those chemicals are being made with refined virgin oil. And they probably will be for the foreseeable future, because oil is so cheap and because the cost to deconstruct the plastic and capture the good molecules is so expensive. But the research shows it's possible to use cast-off plastics as a feedstock for those products, instead of using virgin oil.

"What we did is a proof of concept. We showed you can take it apart and then drive it in a direction you want it to go,'' Robertson said. "But being able to do it economically? That's not feasible yet."

For example, major chemical manufactures have known for years how to turn plastic bottles back into plastic bottles, Robertson noted. But it's still much cheaper to make new bottles out of oil. Cheaper, Robertson notes, but certainly not environmentally sustainable.

So, instead, society recycles some of our bottles into carpeting or fabric for things such as fleece sweaters. But that market absorbs only about 30 percent of all plastic bottles made. And the current melt-process recycling commonly leads to new plastics with inferior properties, called downcycling, that frequently end up in lower-grade applications such carpeting.

The other 70 percent of bottles end up in landfills, their treasure trove of molecules wasted.

Instead of downcycling, the Wisconsin researchers found a system of depolymerized molecules that can be purified and used in higher-value applications.

"If we could figure out a way to mine those plastics instead of burying them in landfills, we end up using less oil and we stop burying valuable chemicals,'' Robertson noted. "We can get there if the economics works. Or if we have policy that values those things."

In March, Chemistry World announced the research team's results in the publication Chemical Communications, the Journal of the Royal Society of Chemistry in London. The project, which took 18 months, was funded by a grant from the Research Corporation for Science Advancement.

Robertson was proud that all of the project's work was done by undergraduate students, such as Eric Kral, who has moved on to graduate school at North Dakota State University.

"The problems with plastics are very apparent in our environment, but the ways to solve those problems are not," Krall said. "My research experience at Northland has inspired me to try to find new innovative ways to solve those issues." ___